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(11) | EP 0 714 062 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Method for providing multiple grades of service with protection against overloads in a shared resources system |
| (57) Techniques for (a) controlling admission of customers to a shared resource, (b) adjusting
the capacity of a resource in light of new customer demand, and (c) diverting usage
from a failed resource to alternative resources, each use a "blocking probability
computer" (BPC) to solve a resource-sharing model that has a product-form steady-state
distribution. The techniques allow each customer to obtain an appropriate grade of
service and protection against overloads from other customers. Each customer is a
source of a series of requests, and is assigned "upper-limit" (UL) and "guaranteed-minimum"
(GM) "bounds" on its requests. The upper limit bound puts an upper limit on the number
of requests from that customer that can be in service at any time. The guaranteed-minimum
bound guarantees that there will always be available resource units in the resources
to serve a specified number of requests from that customer. The desired blocking probabilities
are directly expressed in terms of normalization constants appearing in the product-form
steady-state distribution. The BPC computes the normalization constants by first constructing
the generating function (or z-transform) of the normalizing constant and then numerically
inverting the generating function. |